The invention relates to a micromirror, a micro-oscillating mirror in particular, according to the definition of the species of the main claim.
A micromirror and, in particular, a micro-oscillating mirror which is equipped with an electrostatic drive, has already been described in German Patent Application 198 57 946.2. A largely cantilevered mirror surface having two or possibly four spring connectors or torsion beams arranged opposite each other in pairs is linked to a surrounding support body.
In addition, a micromirror having a magnetic drive is already known from U.S. Pat. No. 5,748,172. A largely cantilevered membrane is also linked to a surrounding support body by two opposite torsion beams, printed conductors being located on the bottom of the mirror surface in the form of conductor loops or windings, through which an electric current may be routed so that when an external magnetic field is applied, a torque is exerted on the mirror surface.
The object of the present invention was to develop a novel mirror design with an increased mechanical load capacity, which, in particular, is also suitable for a magnetic drive. The increased mechanical load capacity is to be attained by designing the torsion beams or spring connectors linking the mirror surface to the support body to be stronger and more resistant to torsions and shocks.
In contrast to the related art, the micromirror according to the present invention has the advantage of a higher mechanical load capacity and higher fracture stability while at the same time relatively low electrical voltages are required to displace the mirror surface from the rest position or to excite it to torsional oscillation.
In addition, the design of the torsion beams according to the present invention advantageously results in higher motive forces overall being required to displace the mirror surface than in known micromirrors, which results in the cited increased stability.
Finally, the fact that, according to the present invention, the mirror surface is linked to the support body by at least two torsion beams arranged at least approximately parallel to each other with comparable bending strength results in reduced torsional stiffness compared to a single torsion beam which occupies the total width of the parallel torsion beams and the intermediate space between them. Consequently, a larger angle of displacement of the mirror surface is possible with an increased stability of the overall mirror design at the same time.
Advantageous refinements of the invention result from the measures cited in the dependent claims.
It is thus advantageous in particular if each of two opposite sides of the mirror surface is linked to the support body by two torsion beams spaced parallel to each other. In this manner, a printed conductor may be applied to the surface of each torsion beam, which may occupy the entire surface of the torsion beam so that the width of the torsion beam is optimally utilized with simultaneous insulation of the printed conductors from each other. It is, in particular, advantageously possible to route particularly high electric currents of, for example 10, mA to 1 A across the printed conductors located on the surface of the torsion beams.
In addition, the printed conductors routed on the surface of the torsion beams may now be made as wide as possible since the problem of electrically insulating them from each other is eliminated.
Overall, the widened printed conductors and the optimum utilization of the surface of the torsion beams thus result in a higher current carrying capacity, which results in higher magnetic forces or torques in the case of a magnetic drive. Therefore, the design of the micromirror according to the present invention now makes it possible to choose a more robust design of the torsion beams due to the greater forces that may be generated.
The total width of the two torsion beams spaced parallel to each other together with the width of the intermediate space between them is now greater than the width of a corresponding single torsion beam known from the related art.
In addition, the torsion stiffness of the spring design of the present invention is advantageously less than the torsion stiffness of a single torsion beam which occupies the total width of the two parallel torsion beams and the associated intermediate space.
Moreover, the spring design presented may also be advantageously transferred to micromirrors having two torsion axes perpendicular to each other.
It is further advantageous that the printed conductors on the surface of the torsion beams, the contact surfaces located on the support body in some areas and the printed conductors routed on the surface of the mirror surfaces may be produced in a simple manner by surface metallization methods which are known per se.
Moreover, the micromirror according to the present invention may be equipped with either an electrostatic or a magnetic drive.
Finally, providing the actual mirror surface with two loops attached symmetrically in the external area resulting in a distinct increase of the magnetic flux, enclosed by the printed conductors routed on the surface of the mirror surface, in an external magnetic field has the advantage that these loops can be used simultaneously as a stop for the mirror surface and consequently the mirror surface and also the torsion beams, in particular, are protected against shocks and overloads of short duration. For this purpose, in the event of excessively high torsion of the mirror surface, it is advantageously provided that the loops strike the upper or lower side of the housing or the support body and thus prevent the torsion beams from breaking.
These additional loops on the mirror surface are advantageous in particular if the micromirror according to the present invention is to be statically displaced and an air gap is provided to attain as little air cushioning as possible between the mirror surface and the surrounding support body.
In summary, the micromirror of the present invention has the advantage of high motive forces with simultaneous low driving voltages, resulting in an improved stability of the micromirror and an increased yield in manufacturing at the same time since the microstructures produced are more robust as a whole. In addition, the micromirror according to the present invention can be produced using manufacturing methods known per se so that no new procedure steps and manufacturing technologies are required in production.